A basic ethical principle for therapy is free will. If your partner does not want to take therapy, the best is not to pressure him/her to do it. You might, however, invite him/her kindly to take two initial sessions to give it a chance and discuss his/her concerns or doubts regarding therapy during the sessions.
You can contribute a lot for him/her to feel safe and not overwhelmed about the idea of therapy. You should, however, never force them or reproach them strongly for not wanting to. Taking therapy is a good resource for many people, but it is not the only solution for solving a problem.